Polytetrafluoroethylene fabrics are fabrics woven from strands of polytetrafluoroethylene. Polytetrafluoroethylene is commonly known as Teflon and is a registered trademark of E. I. DuPont Company.
Polytetrafluoroethylene fabrics are available in many varieties from a variety of distributors. Typical of the polytetrafluoroethylene fabrics is a fabric sold by Stern and Stern Textiles, Incorporated, New York, N.Y., called T41-30. It is a lenoweave cloth with 45.times.21 ends/inch and has a thickness of 0.010 inch. It has a weight of 4.35 ounces per square yard.
Polytetrafluoroethylene fabrics are used for a variety of purposes including such things as filters, screens, reinforcement, packing, insulation, liners and gasket materials.
They are also used as supports for fluoropolymer ion exchange active films. Such films are commonly used as ion exchange membranes in electrolytic cells.
Fluoropolymer fabrics are limp and exhibit low friction, thread to thread. This causes these fabrics to become distorted under normal handling and causes holes to appear without breaking threads.
The prior art has attempted to coat polytetrafluoroethylene fabrics by using mechanical lamination equipment. Other prior art has attempted to attach polytetrafluoroethylene fabrics to ion exchange membrane films using heat treatment and extraction procedures rather than stabilizing the cloth itself (see U.S. Pat. No. 4,272,560).
Other known relevant art is known to include: U.S. Pat. Nos. 3,770,567; 3,925,135; 4,272,560; 4,324,606; 4,399,183; 4,341,605; and 4,437,951.
Burrell states the theory of Bagley [J. Paint Tech., Volume 41, page 495 (1969)] predicts a non-crystalline polymer will dissolve in a solvent of similar solubility parameter without chemical similarity, association, or any intermolecular force. However, he fails to mention anything about the solubility of polymers demonstrating crystallinity.
It would be highly desirable to be able to size polytetrafluoroethylene fabrics. The present invention provides such a method.